Measurement of $Γ_{ee}(J/ψ)$ with KEDR detector

Abstract

The product of the electronic width of the $J/ψ$ meson and the branching fractions of its decay to hadrons and electrons has been measured using the KEDR detector at the VEPP-4M $e^+e^-$ collider. The obtained values are: $Γ_{ee}(J/ψ) = 5.550 \pm 0.056 \pm 0.089 \, \text{keV}, $ $Γ_{ee}(J/ψ) \cdot \mathcal{B}_\text{hadrons}(J/ψ) = 4.884 \pm 0.048 \pm 0.078 \, \text{keV}, $ $Γ_{ee}(J/ψ) \cdot \mathcal{B}_{ee}(J/ψ) = 0.3331 \pm 0.0066 \pm 0.0040 \, \text{keV}.$ The uncertainties shown are statistical and systematic, respectively. Using the result presented and the world-average value of the electronic branching fraction, one obtains the total width of the $J/ψ$ meson: $Γ= 92.94 \pm 1.83 \, \text{keV}.$ These results are consistent with the previous experiments.

19 pages, 13 figures